The Bus Driver Problem

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <queue>
#include <algorithm>
#include <vector>
#include <cstring>
#include <stack>
#include <cctype>
#include <utility>   
#include <map>
#include <string>  
#include <climits> 
#include <set>
#include <string> 
#include <sstream>
#include <utility>
#include <ctime>

using std::priority_queue;
using std::vector;
using std::swap;
using std::stack;
using std::sort;
using std::max;
using std::min;
using std::pair;
using std::map;
using std::string;
using std::cin;
using std::cout;
using std::set;
using std::queue;
using std::string;
using std::istringstream;
using std::make_pair;
using std::greater;

const int MAXN(110);
int arr1[MAXN], arr2[MAXN];

int main()
{
	int n, d, r;
	while(scanf("%d%d%d", &n, &d, &r), n || d || r)
	{
		for(int i = 1; i <= n; ++i)
			scanf("%d", arr1+i);
		for(int i = 1; i <= n; ++i)
			scanf("%d", arr2+i);
		sort(arr1+1, arr1+1+n);
		sort(arr2+1, arr2+1+n);
		int ans = 0;
		for(int i = 1; i <= n; ++i)
			ans += max(arr1[i]+arr2[n-i+1]-d, 0);
		printf("%d\n", ans*r);
	}
	return 0;
}